Gastrointestinal stromal tumor (GIST) represents the most common mesenchymal malignancy of the gastrointestinal (GI) tract. In neurofibromatosis (NF), the increased incidence of tumor needs to be considered even in non-symptomatic individuals. Patients with neurofibromatosis NF type 1 have an increased risk of developing GI tumors including rare types such as GIST. We report a case of GIST in a 53-year-old male patient with neurofibromatosis. The patient was diagnosed with NF four years ago and his medical history revealed that he was hospitalized 5 times with a provisional diagnosis of massive lower gastrointestinal bleeding. GIST was diagnosed at explorative laparotomy and the tumor was 21 cm × 13 cm × 7 cm in size. Immunohistochemical examination showed that vimentin, actin and CD117 were positive. Computerized tomography showed peritoneal implants three months later. Imatinib mesylate (600 mg/d) was initiated. However, control computerized tomography revealed liver and omental metastasis. The dosage was elevated to 800 mg/d. Despite high dosage, the progression of the metastatic lesions continued in the liver and omentum. The patient started oral sunitinib malate (Sutent? Pfizer Inc, New York, NY, USA) 50 mg per day for 4 consecutive weeks, followed by 2 wk off per treatment cycle. The metastatic lesions in the liver and omentum were decreased in size after four courses, suggesting that sunitinib is also an effective treatment modality for metastatic GIST in NF patients. Gastrointestinal stromal tumor (GIST) represents the most common mesenchymal malignancy of the gastrointestinal (GI) tract. In neurofibromatosis (NF), the increased incidence of tumor needs to be considered even in non-symptomatic individuals. Patients with neurofibromatosis NF type 1 have an increased risk of developing GI tumors including rare types such as GIST. We report a case of GIST in a 53-year-old male patient with neurofibromatosis. The patient was diagnosed with NF four years ago and his medical history showed that he was hospitalized 5 times with a provisional diagnosis of massive lower gastrointestinal bleeding. GIST was diagnosed at explorative laparotomy and the tumor was 21 cm × 13 cm × 7 cm in size. Immunohistochemical examination showed that vimentin, actin and CD117 were positive. Computerized tomography showed peritoneal implants three However, control computerized tomography revealed liver and omental me was. Despite the high dosage, the progression of the metastatic lesions continued in the liver and omentum. The patient started oral sunitinib malate (Sutent® Pfizer Inc, New York, NY, USA) 50 mg per day for 4 consecutive weeks, followed by 2 wk off per treatment cycle. The metastatic lesions in the liver and omentum were decreased in size after four courses, suggesting that sunitinib is also an effective treatment modality for metastatic GIST in NF patients.